Fix #12861 Hang in valueFlowCondition() with huge array (danmar#7757)

I tested the fix based on 4617bc2.

Use the cppcheck to check the below code which is submitted on the
ticket #12861.
```
#define ROW A, A, A, A, A, A, A, A,
#define ROW8 ROW ROW ROW ROW ROW ROW ROW ROW
#define ROW64 ROW8 ROW8 ROW8 ROW8 ROW8 ROW8 ROW8 ROW8
#define ROW512 ROW64 ROW64 ROW64 ROW64 ROW64 ROW64 ROW64 ROW64
void f() {
	static const char A = 'a';
	const char a[] = {
		ROW512	ROW512 	ROW512	ROW512
	};
}
```
With the fix, the overall time is 1.52582s.
Without the fix, the time is 25.9674s.

I also tested the testrunner for running the whole of the unit tests.
There is some performance improment with the fix, but not remarkable.

Author: clock999

lib/token.h

@@ -117,6 +117,7 @@ class CPPCHECKLIB Token {
         Token* mAstOperand1{};
         Token* mAstOperand2{};
         Token* mAstParent{};
+        Token* mAstTop{};
 
         // symbol database information
         const Scope* mScope{};
@@ -1557,6 +1558,9 @@ class CPPCHECKLIB Token {
      * @throws InternalError thrown on cyclic dependency
      */
     void astParent(Token* tok);
+    void astTop(Token * tok) {
+        mImpl->mAstTop = tok;
+    }
 
     Token * astOperand1() {
         return mImpl->mAstOperand1;
@@ -1597,13 +1601,19 @@ class CPPCHECKLIB Token {
 
     }
     RET_NONNULL Token *astTop() {
+        if (mImpl->mAstTop) {
+            return mImpl->mAstTop;
+        }
         Token *ret = this;
         while (ret->mImpl->mAstParent)
             ret = ret->mImpl->mAstParent;
         return ret;
     }
 
     RET_NONNULL const Token *astTop() const {
+        if (mImpl->mAstTop) {
+            return mImpl->mAstTop;
+        }
         const Token *ret = this;
         while (ret->mImpl->mAstParent)
             ret = ret->mImpl->mAstParent;

lib/tokenlist.cpp

@@ -1860,6 +1860,16 @@ void TokenList::createAst() const
             throw InternalError(tok, "Syntax Error: Infinite loop when creating AST.", InternalError::AST);
         tok = nextTok;
     }
+    for (Token *tok = mTokensFrontBack->front; tok; tok = tok ? tok->next() : nullptr) {
+        if (tok->astParent())
+            continue;
+        if (!tok->astOperand1() && !tok->astOperand2())
+            continue;
+        visitAstNodes(tok, [&](Token* child) {
+            child->astTop(tok);
+            return ChildrenToVisit::op1_and_op2;
+        });
+    }
 }
 
 namespace {

test/cli/performance_test.py

@@ -221,6 +221,7 @@ def test_slow_many_scopes(tmpdir):
                 }""")
     cppcheck([filename]) # should not take more than ~1 second
 
+
 @pytest.mark.skipif(sys.platform == 'darwin', reason='GitHub macOS runners are too slow')
 @pytest.mark.timeout(20)
 def test_crash_array_in_namespace(tmpdir):
@@ -241,6 +242,28 @@ def test_crash_array_in_namespace(tmpdir):
                 }""")
     cppcheck([filename]) # should not take more than ~5 seconds
 
+
+@pytest.mark.skipif(sys.platform == 'darwin', reason='GitHub macOS runners are too slow')
+@pytest.mark.timeout(20)
+def test_crash_array_in_array(tmpdir):
+    # 12861
+    filename = os.path.join(tmpdir, 'hang.cpp')
+    with open(filename, 'wt') as f:
+        f.write(r"""
+                #define ROW A, A, A, A, A, A, A, A,
+                #define ROW8 ROW ROW ROW ROW ROW ROW ROW ROW
+                #define ROW64 ROW8 ROW8 ROW8 ROW8 ROW8 ROW8 ROW8 ROW8
+                #define ROW512 ROW64 ROW64 ROW64 ROW64 ROW64 ROW64 ROW64 ROW64
+                #define ROW4096 ROW512 ROW512 ROW512 ROW512 ROW512 ROW512 ROW512 ROW512
+                void f() {
+                    static const char A = 'a';
+                    const char a[] = {
+                        ROW4096 ROW4096 ROW4096 ROW4096
+                    };
+                }""")
+    cppcheck([filename])
+
+
 @pytest.mark.timeout(5)
 def test_slow_bifurcate(tmpdir):
     # #14134